Water Pollution Sewage Treatment Video Lecture | Biology for EmSAT Achieve

hello friends this video on
environmental issues part eight is
brought to you by exam feel calm no more
fear from exam so now let us discuss
some of the important causes in little
more detail so the first thing that we
will discuss is sewage sewage is the
wastewater that needs to be removed from
a community for healthy living as I said
it this waste water comes out of each of
our houses on daily basis but that needs
to be removed out of the community so
where we will remove it so where do we
dispose it is it a wise decision to
collect indirectly dispose it off in a
river which is located far away from our
community not at all because even if we
descend into that River so somehow
directly or indirectly that river water
only will come back to us for our
drinking purposes so there is no point
in doing that so what is the wisest way
to handle sewage so disposal of switch
has to be done in a very appropriate way
in appropriate sewage disposal can cause
water pollution and what can happen if
water pollution is caused the water the
same water is used for washing our
clothes for cooking for drinking for
bathing so for all the purposes the same
water is going to be used so do we want
water to get quality not really so how
should we handle proper sewage disposal
so let us see how which is treat it
before it is the post off so sewage
needs to be treated in sewage treatment
plants before disposal
so these sewage treatment plants play a
very important role in controlling water
pollution so let us see what happens
here so the sewage treatment is carried
out in two stages primary treatment and
secondary treatment now what happens in
this street these treatments now
basically the focus in sewage treatment
is that whatever toxic substances are
present in this to which they need to be
converted into less toxic substances so
that is the main agenda so let us see
how do we do that so how is sewage
treatment done that might be your
question
let's quickly see first we will talk
about primary treatment of sewage so
here what we do physically removal of
particles from sewage using the
following processes so here physically
whatever extra particles are present in
the sewage so that needs to be removed
by filtration or sedimentation so
filtration is that process where we
actually when we have a mixture of a
solid and a liquid we pass the mixture
through a filter and the liquid passes
through by the soil it remains over it
so that is how we can separate the solid
and the liquid so in the primary
Streetman of sewage all the solid
particles can be removed from the switch
so this is the first process that is
filtration so here you can see this is
our open to looks like and it has a
value this naked structure is present
which doesn't allow the solid particles
to pass through but it allows the liquid
to pass through it sedimentation is that
process where the substances or the
solid particles are separated from the
solvent on water under the influence of
gravity for example if you can try it
out at your home later suppose if you
take a mug and you put some water and
some mud inside it now just leave it for
some time what happens you see that the
mud stands at the water and the water
remains at the top so if you want to
separate the water
mind what you can do if you leave it for
some time now when you see that the
particles have set at the bottom so here
you can see these are the particles and
you have the liquid here liquid or water
or solvent whatever that is there so
everything is you can just pour out the
solvent in some other vessel so at least
you got rid of the bigger particles so
these are the two methods by which the
particles which are present in the
sewage can be physically removed from
the sewage and this is called primary
treatment of sewage so filtration and
sedimentation as I mentioned filtration
separation of a solid from liquid by
passing it through pores of a filter so
you can click off the seal which you use
by while you prepare tea so when you
prepare tea you filter the team before
you drink it right so that then you use
a seed like this so that is also a type
of filtration so in laboratory you use a
filter something of this sort
so here when you filter it you actually
are left with the solid particles here
so here you have the solid particles and
the liquid passes through it and in
sedimentation what happens the particles
will settle out at the bottom under the
influence of gravity so here you see
first the particle was present
everywhere but when you leave it for
some time after some time T you see that
the particle settle at the bottom and
the clear fluid will remain at the top
so that's how you can separate the two
so this was the primary treatment now
let's come to the secondary treatment
now the secondary treatment starts after
primary filter so now you have already
separated two solid particles so now
what you have to do is now out of that
liquid sewage you need to remove the
harmful substances so now it is the most
engine task so let's see how do we do
this so here the affluent from library
treatment is passed on for secondary
treatment so whatever we receive what is
affluent now in sedimentation the
solvent which remains above that is one
affluent so this in fluent will now move
for secondary treatment and what will
happen here constant agitation of the
influence of the affluent is agitated it
is mixed or it is constantly it is
educated it is moved and it is mixed air
is also pumped into the camp or a
widening POC air there is a purpose
behind that because now microorganisms
are going to play a role in the
secondary treatment now for
microorganisms to live they need some
air so that they can undergo a roving
respiration so therefore we have pumped
in air into the tank this air will lead
the presence of air will lead to
vigorous growth of aerobic microbes and
that is what we wanted now you might be
surprised and why do we want micro to
present there that's because my groups
will be able to solve our problem
microbes consume organic matter so now
whatever organic matter is present
inside the sewage that will be consumed
by the microbes so that organic matter
is not disposed off into the water
because the organic matter is something
which is biodegradable so if it goes
into the water gets mixed with the water
for use the water there is no point so
we can get the organic matter removed
before it is disposed so these
microorganisms will start consuming the
organic matter
now what happens once the organic market
is consumed your sewage is actually
becoming cleaner with granny treatment
followed by secondary treatment so here
comes the concept of d-o-d that is
biochemical oxygen demand so what is
they
sweetie see so biochemical oxygen demand
it is like a parameter which determines
that purity of water or which determines
the amount of harmful substances that
have been removed from water
now while suddenly are we talking about
VOD so B or D is basically a measure
which tells us till when do we need to
continue with the secondary treatment of
sewage now as you can see that in
primary treatment what do we do we just
remove the solid particles from the
sewage and in the secondary treatment
what we actually do is we allow the
microorganisms to grow and we let them
consume all the organic matter present
in the search but how do we know that
how much or to what extent has the
sewage being purified or or till autumn
how how much extend the toxicity have
been reduced so VOD is a measure to
which lets us know when to stop the
secondary treatment so it is the amount
of oxygen needed by aerobic organisms in
water to break the organic material in
water at a particular temperature over a
period of time so what we have done is
we have allowed some microorganisms
which are aerobic to grow there so they
are what are they doing they are
constantly utilizing oxygen so we can
measure the amount of oxygen that is
being used by them correct so the amount
of oxygen gradually will start reducing
because they are people granule sensors
continuously using it and why are we
using it to break down the organic
material which is present in the water
and a particular temperature over a
period of time so this b OD can give us
a hint that okay this much amount of
oxygen has been used that means this
much amount of it will give us a rough
idea that will give this much amount of
organic material have already been
broken down so we will get to know how
much of a toxic and in how much toxic AP
has been reduced so lessen the value of
b OD lesser is in spawn using potential
so the smaller the value is the less
pollutant it is that means the less
harmful it is so when the value of
beauty reaches a considerably lower
value then we can stop the secondary
treatment of sewage and then the sewage
is ready for disposal into any water
water so secondary treatment is
continued till Bo d is considerably
reduced
now just see how important the treatment
of sewage is because when you treat the
sewage now you know that there are no
solid particles in the sewage because
they have been removed in primary
treatment you also know that there are
no organic matter in it because there
has been removed during secondary
treatment so now if you will dispose the
same sewage directly into a water body
it is not going to cause that much of
harm so the difference in the extent of
water pollution is huge so that is why
it is extremely important that the
student should be properly treated
before it is disposed of in water
bottles now the question is what happens
once the Bo D is significantly reduced
as I said once it reduces significantly
we stop secondary treatment and what do
we do so now the influent will be passed
on to a settling tanks there is another
tank called settling tank and here the
bacterial masses sediment and the bottom
forming activated sludge so those
microorganisms which were playing a
major role up till now they all been
sediment at the bottom and this group
this thing which is formed at the bottom
of the sediment is known as
activated sludge you can see this is the
aeration tank where air was being pumped
in and the microorganisms were growing
and they were utilizing or raking down
the organic matter
now once the bad Bo D is reduced
significantly it is passed on to the
settling tank that is the stand and here
the bacteria will settle down at the
bottom see here you can see so this
settlement at the bottom is known as
activated sludge so this is activated
sludge so this sludge is then taken out
for further sludge treatment because
this again contains a lot of bacteria so
it can stay in for further to evening
whereas the water which is present on
the top row is clear that water is taken
out and this is the treated water or
treated switch so this camp it is posed
off into any water body now what what do
we do with activated sludge as I said
this is passed back into the aeration
tank as you can see here we'll pass it
back to the aeration tank because they
contain bacteria and in the aeration
tank we need bacteria and the remaining
passed onto an aerobic sludge digesters
now some of them are passed into
anaerobic digesters where the sludge
gets digested and aerobic very that is
an absence of oxygen so influent from
the settling-down is released in two
water bottles so I hope with this it is
clear to you that how humid should be
treated and how important is sewage
treatment now how does shoe is
discharged harm aquatic life now as I
had mentioned that sewage is something
if you without treating it if you direct
it is supposed to into a water body what
can it do to the aquatic life sewage
discharge into what your body's microbes
cause death biodegradation of so what
happens is if the sewage is discharged
into water bodies now this sewage
contains a lot of organic matter
as I mentioned just now now what will
happen is the microorganisms they can
start degrading the organic method they
will start breaking down the organic
matter and in order to do that they
would need an oxygen right because these
are the aerobic microbes which are able
to biodegrade the organic matter now
when they start using up a lot of oxygen
and what happens all the oxygen which is
present in the dissolved form in water
they are mostly used up by the microbes
so the microbes actually use up all the
oxygen and finally then there is a lack
of oxygen for the equity flight like
even fishes need oxygen even the aquatic
plants need oxygen but since most of the
oxygen is being used up by the microbes
so there is lack of oxygen for these a
training life and this then threaten the
rapid decline and then even kill them so
this is how the switch discharged and
harmed the aquatic life thank you please
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